respi

• Respiratory System


  System responsible for delivering oxygen to cells and removing carbon dioxide
• Human cells utilize oxygen and produce carbon dioxide in carrying out metabolic processes
• To deliver oxygen and eliminate carbon dioxide, exchange of gases must occur
• Component Organs of Respiratory System

  • Lungs
  • Nose
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
• Lungs


  • One pair, left and right
• Conducting Portion of Respiratory System

  • Nose
  • Pharynx
  • Larynx
  • Trachea
  • Main bronchi
• Conducting Portion

  Transports air, filters, moistens, and warms inspired air before it reaches the respiratory portion
• Nose

  Hollow organ divided into two nasal cavities by a nasal septum, bounded by anterior naris (nostril) and posterior naris (continuous with pharynx)
• Nose


  • Framework of walls, roof and floor formed partly by bone and partly by cartilage
  • Mucosa lines the luminal surface, consisting of epithelium and underlying loose connective tissue (lamina propria)
• Regions of Nose

  • Vestibule
  • Nasal mucosa
• Vestibule


  Lined by skin with coarse and stiff hair that acts as a gross filter for inhaled air
• Nasal mucosa

  Lined by respiratory epithelium (ciliated pseudostratified columnar epithelium with goblet cells), except roof which is lined by olfactory epithelium<|>Lamina propria contains mucous and serous glands, mast cells, and MALT
• Respiratory epithelium

  Lines not only the nasal cavity but also most of the conducting portion of the respiratory system<|>Consists of 6 cell types: ciliated columnar, goblet, brush, serous, basal, and granule (Kulchitsky) cells
• Olfactory epithelium

  Found at the roof of the nasal cavity, over the superior turbinate and adjacent parts of the nasal septum<|>Yellowish brown epithelium due to lipofuschin pigments in the cytoplasm of sustentacular/supporting cells
• Cell types in Olfactory Epithelium

  • Olfactory cells (spindle shaped bipolar neurons)
  • Sustentacular/supporting cells (50-60 um tall columnar cells)
  • Basal cells (short, basophilic, pyramid-shaped)
• Paranasal Sinuses

  • Frontal
  • Maxillary
  • Ethmoidal
  • Sphenoidal
• Paranasal Sinuses


  Walls lined by mucous membrane and respiratory epithelium (thinner and lesser goblet cells)<|>Make the face less heavy by reducing its bony mass
• Pharynx


  Funnel shaped fibromuscular tube, subdivided into 3 regions: nasopharynx, oropharynx, and laryngopharynx
• Histologic Layers of Pharynx

  • Mucosa (epithelium and lamina propria)
  • Submucosa (loose connective tissue)
  • Muscularis externa
  • Adventitia (loose connective tissue)
• Larynx


  Situated between the pharynx and the trachea, responsible for phonation<|>Formed by 3 unpaired (thyroid, cricoid, epiglottic) and 3 paired (corniculate, cuneiform and arytenoid) cartilages
• Larynx


  Internal surface lined by mucous membrane, with respiratory epithelium except over the anterior surface and upper half of posterior surface which is lined by nonkeratinized stratified squamous
• Trachea


  Tube that extends from the cricoid cartilage to the lungs, reinforced by 10-12 horseshoe-shaped hyaline cartilage rings
• Histologic Layers of Tracheal Wall

  • Mucosa
  • Submucosa
  • Cartilage and muscle layer
  • Adventitia
• Primary (extrapulmonary) Bronchi


  Identical to trachea, except smaller in diameter and thinner walls, located outside the lungs
• Bronchial Tree (Intrapulmonary)


  • Secondary bronchi (supplies lung lobe)
  • Tertiary bronchi (supplies bronchopulmonary segment)
  • Bronchioles (supplies lung lobule)
  • Terminal bronchioles
  • Respiratory bronchioles
• Bronchioles


  Less than 1mm in diameter, walls of epithelium remain ciliated but progressively becomes cuboidal distally, contain Clara cells
• Terminal Bronchioles


  Arise from bronchioles, less than 0.5 mm in diameter, constitute the terminus of the conducting portion
• Respiratory Bronchioles


  Arise from terminal bronchioles, similar in structure but with thin-walled, pouch-like structures called alveoli
• Alveoli


  Arise individually or in clusters (alveolar sacs) from either respiratory bronchioles or alveolar ducts, open on one side to allow entry of gases
• Epithelial Cells of Interalveolar Septum


  • Type I alveolar cell (pulmonary epithelial cell; pneumonocyte type I)
  • Type II alveolar cell (great alveolar cell, pneumonocyte type II)
• Blood-Air Barrier


  Ultra-thin structure separating blood in pulmonary capillary from air in alveoli, consisting of pneumocyte type 1, basal laminae of alveolar epithelium and capillary endothelium, and capillary endothelial cell
• Lungs

  • Pair of conical organs occupying greater part of thoracic cavity, separated by mediastinum, divided by fissures into lobes (left 2, right 3)
• Pleural Cavities

  Thoracic cavity lined by serous membranes (pleura), with visceral pleura covering lungs and parietal pleura lining thoracic walls, space between is pleural cavity containing serous fluid